Detailed Description

A structure holding meteorological information, excluding precipitation

Public Member Functions
	Weather (double T=15.0, double Tmax=17.0, double Tmin=13.0, double rH=70.0, double wind=2.0, double sunshine=0.5, double Rs=15, double Ra=30, double daylength=12)
	Creates a "weather" from given data.

Weather	operator* (double factor)
	Multiply.

Weather &	*operator=** (double factor)
	inplace multiplication

Weather	operator+ (const Weather &w)
	add operator

Weather &	operator+= (const Weather &w)
	inplace add

double	Rn (double albedo, bool daily=false) const
	Calculates the net radiation flux \(R_n \left[\frac{MJ}{m^2 day}\right]\).

std::string	to_string () const
	Returns a string representation.

Static Public Member Functions
static double	get_snow_threshold ()
	Returns the actual snow threshold value in degC.

static void	set_snow_threshold (double new_threshold)
	Sets the snow threshold globally for cmf.

Public Attributes
double	e_a
	Actual vapor pressure \(e_a\ [kPa]\).

double	e_s
	Saturated vapor pressure in \(e_s [kPa]\).

double	instrument_height
	length of the day in h

double	Ra
	Extra terrestrial radiation \(R_s \left[\frac{MJ}{m^2 day}\right]\).

double	Rs
	Global Radiation in \(R_s \left[\frac{MJ}{m^2 day}\right]\).

double	sunshine
	Fractional sunshine duration (per potential sunshine duration) \(\frac n N\ [-]\).

double	T
	actual Temperature \(T \left[^\circ C\right]\)

double	Tground
	actual Temperature of the ground

double	Tmax
	Maximum daily Temperature \(T_{max} \left[^\circ C\right]\).

double	Tmin
	daily minimum Temperature \(T_{min} \left[^\circ C\right]\)

double	Windspeed
	Windspeed \(u \left[\frac{m}{s}\right] \).

Constructor & Destructor Documentation

◆ Weather()

Weather	(	double	T = 15.0,
		double	Tmax = 17.0,
		double	Tmin = 13.0,
		double	rH = 70.0,
		double	wind = 2.0,
		double	sunshine = 0.5,
		double	Rs = 15,
		double	Ra = 30,
		double	daylength = 12 )

Creates a "weather" from given data.

Parameters

T	actual Temperature in deg C
Tmax	daily maximum Temperature in deg C
Tmin	daily minimum Temperature in deg C
rH	actual relative humidity in % [0..100]
wind	actual wind speed in m/s
sunshine	actual fraction of sunshine duration per potential sunshine duration in h/h
Rs	actual incoming shortwave global radiation in MJ/(m2 day)
Ra	actual extraterrestrial shortwave global radiation in MJ/(m2 day)
daylength	length of the day in h

Member Function Documentation

◆ Rn()

double Rn	(	double	albedo,
		bool	daily = false ) const

Calculates the net radiation flux \(R_n \left[\frac{MJ}{m^2 day}\right]\).

\begin{eqnarray*} R_{n} = R_{ns} - R_{nl} \\ \mbox{ Net short wave radiation: }R_{ns} = (1-\alpha) R_s \\ \mbox{ Net long wave radiation: }R_{nl} = R_{black}\ \beta_{v}\ \beta_{c} \\ \mbox{Black body radiation: } R_{black} = \left\{\begin{array}{cl} \sigma T^4 & \mbox{for less than daily time steps} \\ \sigma \frac {T_{max}^4 + T_{min}^4} 2 & \mbox{for daily time steps} \end{array} \right. \\ T = \mbox{Temperature }[K] \\ \sigma = 4.903\ 10^{-9} \frac{MJ}{K^4 m^2 day} \mbox{ Stefan-Boltzmann constant } \\ \mbox{Long wave reflectance: } \\ \mbox{by water vapor: }\beta_{v} = 0.34 - 0.14 \sqrt{e_a} \\ \mbox{ by clouds: }\beta_{c} = 0.1 + 0.9 \frac n N \end{eqnarray*}

Parameters

albedo	the albedo \(\alpha\) of the surface
daily	If true, the net radiation for daily averages will be calculated

Member Data Documentation

◆ instrument_height

double instrument_height

length of the day in h

Height of the measuring instuments above the vegetation